CDC Confirms That Zika Virus Causes Microcephaly in Newborns


By Michelle Mukonyora

14 April 2016

The Centre for Disease Control (CDC) has now confirmed that there is a causal link between the Zika virus and microcephaly. Microcephaly is a rare genetic defect that manifests as babies born with an abnormally small head, and brain defects (Figure 1). Microcephaly in turn has an effect on the development of the foetus.

Amongst other things, researchers found the Zika virus in the brain tissue of foetuses and infants born to infected mothers. They applied these findings to a research framework known as Shepard’s Criteria, which is typically used to determine whether something is the cause of a disease. It supported that Zika is the cause of microcephaly. The cause and effect relationship between the two will serve as a better guide for researchers in their search for a vaccine. Furthermore, it will help public health officials disseminate more concrete statements and safety guidelines for those at risk.

Photo credit: Felipe Dana

Zika is potentially the cause of a host of other foetal abnormalities, and studies are continually being carried out to determine if that is the case. Zika not only affects foetuses, but neurological damage has also been observed in adults. Another study recently showed that Zika is responsible for the Guillain-Barré syndrome, which is a neurological condition. Guillain-Barré causes amongst other things, difficulty in breathing and paralysis. Another serious condition that has symptoms similar to multiple sclerosis has also been reported.

Figure 1: Illustration of baby with microcephaly Image from the Center for Disease Control website (

Thankfully, health officials had been already been advising women in Zika areas to avoid pregnancy as well as infected people to engage in safe sex, as the virus may also be sexually transmitted. However, contraceptives are not readily available to a lot of women in Latin America and a lot of work needs to be done in this respect. This burden lies not just on health officials, but also on religious leaders, as religious beliefs prevent many women from accessing birth control. A further advised precaution is that men infected with Zika should wait at least six months before engaging in unprotected sex. ​

The full research article by Sonja Rasmussen, and published in the New England Journal of Medicine can be found here: Rasmussen et al. (April 13 2016) Zika Virus and Birth Defects – Reviewing the Evidence for Causality. New England Journal of Medicine. DOI:10.1056/NEJMsr1604338